diff --git a/packages/morpho-ts/src/format/format/README.md b/packages/morpho-ts/src/format/format/README.md
index 9f40278d..73faeb69 100644
--- a/packages/morpho-ts/src/format/format/README.md
+++ b/packages/morpho-ts/src/format/format/README.md
@@ -22,7 +22,8 @@ The `format` object provides access to different formatters:
 
 ### Usage
 
-Each formatter can be accessed through the `format` object and provides chainable methods to customize the output. The formatted value can be optained calling `.of(value)` for `number` or `.of(value, decimals)` for `bigint`.
+Each formatter can be accessed through the `format` object and provides chainable methods to customize the output. The formatted value can be obtained calling `.of(value)` for `number` or `.of(value, decimals)` for `bigint`.
+The return value will retain the nullability of the input value, unless a `.default()` method is applied (refer to [Number Formatter](#2-number-formatter) for details).
 
 > [!Tip]
 > You can store the populated `of` function in a custom formatter:
@@ -33,6 +34,7 @@ Each formatter can be accessed through the `format` object and provides chainabl
 > formatDollar(123456789n, 4); // "$12.34k"
 > ```
 
+
 ### 1. Hex Formatter
 
 Formats a value as a hexadecimal string.
@@ -69,6 +71,7 @@ const numberValue = format.number.of(123.45); // "123.45"
 - `.unit(string)`: Adds a unit to the number (e.g., "$", "%").
 - `.locale(string)`: Formats the number according to the specified locale.
 - `.readable()`: Makes the value more readable for small numbers.
+- `.default(string)`: Sets a default value in case value is `null` or `undefined`.
 
 ### 3. Commas Formatter
 
diff --git a/packages/morpho-ts/src/format/format/format.test.ts b/packages/morpho-ts/src/format/format/format.test.ts
index 7aa2cbcf..72982719 100644
--- a/packages/morpho-ts/src/format/format/format.test.ts
+++ b/packages/morpho-ts/src/format/format/format.test.ts
@@ -10,6 +10,10 @@ describe("format", () => {
       it("without option", () => {
         expect(format.hex.of(number)).toEqual((123456789).toString(16));
       });
+      it("with a default value", () => {
+        expect(format.hex.default("default").of(undefined)).toEqual("default");
+        expect(format.hex.default("default").of(null)).toEqual("default");
+      });
     });
     describe("should properly format bigint in hex format", () => {
       it("without option", () => {
@@ -17,6 +21,12 @@ describe("format", () => {
           (123456789).toString(16),
         );
       });
+      it("with a default value", () => {
+        expect(format.hex.default("default").of(undefined, 18)).toEqual(
+          "default",
+        );
+        expect(format.hex.default("default").of(null, 18)).toEqual("default");
+      });
     });
   });
 
@@ -60,6 +70,12 @@ describe("format", () => {
         expect(format.number.of(1.234e30)).toEqual("1234" + "0".repeat(27));
         expect(format.number.of(1.234e2)).toEqual("123.4");
       });
+      it("with a default value", () => {
+        expect(format.number.default("default").of(undefined)).toEqual(
+          "default",
+        );
+        expect(format.number.default("default").of(null)).toEqual("default");
+      });
     });
     describe("should properly format bigint in number format", () => {
       it("without option", () => {
@@ -103,6 +119,14 @@ describe("format", () => {
           "12345,6789",
         );
       });
+      it("with a default value", () => {
+        expect(format.number.default("default").of(undefined, 18)).toEqual(
+          "default",
+        );
+        expect(format.number.default("default").of(null, 18)).toEqual(
+          "default",
+        );
+      });
     });
   });
 
@@ -140,6 +164,12 @@ describe("format", () => {
       it("with locale", () => {
         expect(format.short.locale("fr-FR").of(number)).toEqual("12,3456789k");
       });
+      it("with a default value", () => {
+        expect(format.short.default("default").of(undefined)).toEqual(
+          "default",
+        );
+        expect(format.short.default("default").of(null)).toEqual("default");
+      });
     });
     describe("should properly format bigint in short format", () => {
       it("without option", () => {
@@ -195,6 +225,12 @@ describe("format", () => {
           // the correct space in fr-FR is narrow no-break space (U+202F)
         ).toEqual("1\u202F234,56789");
       });
+      it("with a default value", () => {
+        expect(format.short.default("default").of(undefined, 18)).toEqual(
+          "default",
+        );
+        expect(format.short.default("default").of(null, 18)).toEqual("default");
+      });
     });
   });
 
@@ -229,6 +265,12 @@ describe("format", () => {
           "12\u202F345,6789",
         );
       });
+      it("with a default value", () => {
+        expect(format.commas.default("default").of(undefined)).toEqual(
+          "default",
+        );
+        expect(format.commas.default("default").of(null)).toEqual("default");
+      });
     });
     describe("should properly format bigint in commas format", () => {
       it("without option", () => {
@@ -273,6 +315,14 @@ describe("format", () => {
           "12\u202F345,6789",
         );
       });
+      it("with a default value", () => {
+        expect(format.commas.default("default").of(undefined, 18)).toEqual(
+          "default",
+        );
+        expect(format.commas.default("default").of(null, 18)).toEqual(
+          "default",
+        );
+      });
     });
   });
 
@@ -306,6 +356,12 @@ describe("format", () => {
           "1234567,8900",
         );
       });
+      it("with a default value", () => {
+        expect(format.percent.default("default").of(undefined)).toEqual(
+          "default",
+        );
+        expect(format.percent.default("default").of(null)).toEqual("default");
+      });
     });
     describe("should properly format bigint in percent format", () => {
       it("without option", () => {
@@ -346,6 +402,14 @@ describe("format", () => {
           "1234567,8900",
         );
       });
+      it("with a default value", () => {
+        expect(format.percent.default("default").of(undefined, 18)).toEqual(
+          "default",
+        );
+        expect(format.percent.default("default").of(null, 18)).toEqual(
+          "default",
+        );
+      });
     });
   });
 });
diff --git a/packages/morpho-ts/src/format/format/format.ts b/packages/morpho-ts/src/format/format/format.ts
index 4f1f3616..bdb4c5a9 100644
--- a/packages/morpho-ts/src/format/format/format.ts
+++ b/packages/morpho-ts/src/format/format/format.ts
@@ -8,8 +8,12 @@ enum Format {
   percent = "percent",
 }
 
-interface BaseFormatOptions {
+interface UniversalFormatOptions {
   format: Format;
+  default?: string;
+}
+
+interface BaseFormatOptions extends UniversalFormatOptions {
   digits?: number;
   removeTrailingZero?: boolean;
   min?: number;
@@ -24,7 +28,7 @@ interface FormatShortOptions extends BaseFormatOptions {
   format: Format.short;
   smallValuesWithCommas?: boolean;
 }
-interface FormatHexOptions {
+interface FormatHexOptions extends UniversalFormatOptions {
   format: Format.hex;
   prefix?: boolean;
 }
@@ -260,14 +264,32 @@ function formatBI(
   return formattedValue;
 }
 
+type FormatterWithDefault<F extends BaseFormatter> = {
+  of(value: bigint | null | undefined, decimals: number): string;
+  of(value: number | null | undefined): string;
+} & Omit<F, "of">;
+
 export abstract class BaseFormatter {
   protected abstract _options: FormatOptions;
 
   constructor() {}
 
-  of(value: bigint, decimals: number): string;
-  of(value: number): string;
+  default(_d: string) {
+    this._options.default = _d;
+
+    return this as FormatterWithDefault<this>;
+  }
+
+  of<T extends bigint | null | undefined>(
+    value: T,
+    decimals: number,
+  ): Exclude<T, bigint> | string;
+  of<T extends number | null | undefined>(
+    value: T,
+  ): Exclude<T, number> | string;
   of(value: bigint | number, decimals?: number) {
+    if (value == null) return this._options.default ?? value;
+
     if (typeof value === "number") {
       const str = value.toString();
       const [significant, exp] = str.split(/[eE]/);