> ## Documentation Index
> Fetch the complete documentation index at: https://docs.blockscout.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Tax Calculator

## Calculate my taxes — fetching full history with Blockscout PRO API

<Note>
  This example uses REST methods with the PRO API. See the [PRO API overview](/devs/pro-api) for information on creating and using an API key.
</Note>

You can use the Blockscout API to collect you activity across multiple chains and feed into an existing tax tool (or vibe code your own!).

The recommended approach combines pulling transactions from several feeds and combining them into a single data source.

In the typescript example at the end we follow this basic flow:

1. get supported chains
2. resolve → filter mainnets
3. fetch 1-year history per chain
4. merge + dedupe
5. output rows

## Endpoint Summary

The following REST calls can be used to get tax data. Note that `api/v2 `calls require a working PRO API key.

| Handle                                                            | Why                                     |
| ----------------------------------------------------------------- | --------------------------------------- |
| `GET /api/json/config`                                            | Get all supported chain IDs             |
| `GET https://chains.blockscout.com/api/chains?chain_ids=...`      | Resolve + filter mainnets               |
| `GET /{chainid}/api/v2/addresses/{address}/transactions`          | Top-level txs (fees + native transfers) |
| `GET /{chainid}/api/v2/addresses/{address}/internal-transactions` | Native value inside contract execution  |
| `GET /{chainid}/api/v2/addresses/{address}/token-transfers`       | ERC20 / NFT movements                   |

### Pull and Combine 3 feeds

**Transactions**

```text theme={null}
curl "https://api.blockscout.com/1/api/v2/addresses/0xYOURADDRESS/transactions?apikey=YOUR_KEY"
```

**Internal transactions**

```text theme={null}
curl "https://api.blockscout.com/1/api/v2/addresses/0xYOURADDRESS/internal-transactions?apikey=YOUR_KEY"
```

**Token transfers**

```text theme={null}
curl "https://api.blockscout.com/1/api/v2/addresses/0xYOURADDRESS/token-transfers?apikey=YOUR_KEY"
```

Complete the following programatically.

* join by tx hash
* deduplicate
* normalize

## Pagination

REST responses use keyset pagination.

When a response includes `next_page_params`, copy that object and append its fields to the next request.

Example (params may include additional items such as value, hash, and date inserted that you won't use):

```json theme={null}
{
  "items": [ ... ],
  "next_page_params": {
    "block_number": 24464759,
    "index": 284,
    "items_count": 50
  }
}
```

Next request:

```bash theme={null}
curl "https://api.blockscout.com/1/api/v2/addresses/0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045/transactions?block_number=24464759&index=284&items_count=50&apikey=YOUR_KEY"
```

Then repeat the same pattern with the new `next_page_params` from that response until empty

***

## TypeScript example

```ts theme={null}
const API_KEY = process.env.API_KEY!;
const ADDRESS = "0x...";
const PRO = "https://api.blockscout.com";

async function getJson(url: string) {
  const res = await fetch(url, { headers: { Authorization: API_KEY } });
  return res.json();
}

async function* paginate(url: string) {
  const u = new URL(url);

  while (true) {
    const data = await getJson(u.toString());

    for (const item of data.items) yield item;

    if (!data.next_page_params || !Object.keys(data.next_page_params).length) break;

    for (const [k, v] of Object.entries(data.next_page_params)) {
      u.searchParams.set(k, String(v));
    }
  }
}

async function main() {
  const cfg = await getJson(`${PRO}/api/json/config`);
  const chainIds = Object.keys(cfg.chains);

  const chains = await getJson(
    `https://chains.blockscout.com/api/chains?chain_ids=${chainIds.join(",")}`
  );

  const mainnets = Object.entries(chains)
    .filter(([, c]: any) => !c.isTestnet)
    .map(([id]) => id);

  for (const chainId of mainnets) {
    const base = `${PRO}/${chainId}/api/v2`;

    for await (const tx of paginate(`${base}/addresses/${ADDRESS}/transactions?apikey=${API_KEY}`)) {
      console.log("TX", chainId, tx.hash);
    }

    for await (const t of paginate(`${base}/addresses/${ADDRESS}/token-transfers?apikey=${API_KEY}`)) {
      console.log("TOKEN", chainId, t.transaction_hash);
    }

    for await (const itx of paginate(`${base}/addresses/${ADDRESS}/internal-transactions?apikey=${API_KEY}`)) {
      console.log("INTERNAL", chainId, itx.transaction_hash);
    }
  }
}

main();
```