Model collections lost on form submission

Using the post query below the model returns null for both collections, but it correctly returns the boolean attribute. My guess was that the collections loaded into the model at the time of the pull request would persist in the post request. What am I missing?

EDIT: Basically I am trying to update the invoice list based on the users' select list and checkbox.

Controller:

    [HttpGet]
    [AllowAnonymous]
    public async Task<ActionResult> Index(bool displayFalse = true)
    {
        InvoiceViewModel invoiceView = new InvoiceViewModel();
        var companies = new SelectList(await DbContext.Company.ToListAsync(), "CompanyID", "Name").ToList();
        var invoices = await DbContext.Invoice.Where(s => s.Paid.Equals(displayFalse)).ToListAsync();

        return View(new InvoiceViewModel { Companies = companies,Invoices = invoices, SelectedCompanyID = 0, DisplayPaid = displayFalse});
    }

    [HttpPost]
    [AllowAnonymous]
    public async Task<IActionResult> Index(InvoiceViewModel model)
    {
        model.Invoices = await DbContext.Invoice.Where(s => s.CompanyID.Equals(model.SelectedCompanyID) && s.Paid.Equals(model.DisplayPaid)).ToListAsync();

        return View(model);         
    }

      

        
        
        
      

    

Model:

public class InvoiceViewModel

{

    public int SelectedCompanyID { get; set; }

    public bool DisplayPaid { get; set; }

    public ICollection<SelectListItem> Companies { get; set; }

    public ICollection<Invoice> Invoices{ get; set; }

}

      

        
        
        
      

    

View:

@model InvoiceIT.Models.InvoiceViewModel
<form asp-controller="Billing" asp-action="Index" method="post" class="form-horizontal" role="form">
<label for="companyFilter">Filter Company</label>
<select asp-for="SelectedCompanyID"  asp-items="Model.Companies"  name="companyFilter"  class="form-control"></select>
<div class="checkbox">
    <label>
        <input type="checkbox" asp-for="DisplayPaid" />Display Paid  
        <input type="submit" value="Filter" class="btn btn-default" />     
    </label>
</div>
<br />
</form>
<table class="table">
<tr>
    <th>
        @Html.DisplayNameFor(model => model.Invoices.FirstOrDefault().InvoiceID)
    </th>
    <th>
        @Html.DisplayNameFor(model => model.Invoices.FirstOrDefault().CompanyID)
    </th>
    <th>
        @Html.DisplayNameFor(model => model.Invoices.FirstOrDefault().Description)
    </th>
    <th>
        @Html.DisplayNameFor(model => model.Invoices.FirstOrDefault().InvoiceDate)
    </th>
    <th>
        @Html.DisplayNameFor(model => model.Invoices.FirstOrDefault().DueDate)
    </th>
    <th>
        @Html.DisplayNameFor(model => model.Invoices.FirstOrDefault().Paid)
    </th>
    <th></th>
</tr>

@foreach (var item in Model.Invoices)
{
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.InvoiceID)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.CompanyID)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Description)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.InvoiceDate)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.DueDate)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Paid)
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id = item.InvoiceID }) |
            @Html.ActionLink("Details", "Index", "InvoiceItem", new { id = item.InvoiceID }) |
            @Html.ActionLink("Delete", "Delete", new { id = item.InvoiceID })
        </td>
    </tr>
}
</table>