How to add object with relationship in the DB with redux

I have a billingCycle object with have a list of credits and debts objects that the state would looks like this:

billingCycle: {
  id: 1,
  name: 'March',
  month: 3,
  year: 2022,
  credits: [
    {
      id: 1,
      name: 'Salary',
      value: 3700
    }
  ],
  debts: [
    {
      id: 1,
      name: 'Car fix',
      value: 450
    }
  ]
 }

But I read in Redux docs that this is a bad practice and it’s recommended to use normalized states. So my reducers looks like this:

const INITIAL_STATE = { list: [], billingCycle: {}, credits: [], debts: [] };


export default function (state = INITIAL_STATE, action) {
  switch (action.type) {
    case "BILLING_CYCLES_FETCHED":
      return { ...state, list: action.payload };
    case "BILLING_CYCLES_CREATED":
      return { ...state, billingCycle: action.payload };
    case "BILLING_CYCLES_READED":
      return { ...state, billingCycle: action.payload };
    case "BILLING_CYCLES_UPDATED":
      return { ...state };
    case "BILLING_CYCLES_REMOVED":
      return { ...state };
    case "CREDIT_ADDED":
      return { ...state, credits: state.credits.concat(action.payload) };
    case "CREDIT_REMOVED":
      return { ...state, credits: state.credits.splice(action.payload, 1) };
    case "DEBT_ADDED":
      return { ...state, debts: state.debts.concat(action.payload) };
    case "DEBT_REMOVED":
      return { ...state, debts: state.debts.splice(action.payload, 1) };
    case "RETURN_STATE":
      return { ...state };
    default:
      return state;
  }
}

And this is my create action:

export function create(billingCycle) {
  axios.post(`${BASE_URL}/billingCycles`, billingCycle);
  return {
    type: "BILLING_CYCLES_CREATED",
    payload: billingCycle
  };
}

My question is: how can I send a billingCycle object to the API call with credits and debts with it? The create method only add the billingCycle without it. How can I map the respective objects related with it to the object? Where in my code I do this integration?