发票管理系统风险防控：虚开发票识别 / 超期认证预警 / 重复报销拦截（附案例）

// 虚开发票检测算法示例
public class FakeInvoiceDetector
{
    public bool DetectAbnormalPattern(Invoice invoice)
    {
        // 校验发票基本信息
        if (!ValidateBasicInfo(invoice))
            return true;
            
        // 检查开票频率异常
        if (CheckFrequencyAbnormal(invoice.SellerTaxId))
            return true;
            
        // 验证金额模式异常
        if (CheckAmountPattern(invoice))
            return true;
            
        return false;
    }
    
    private bool ValidateBasicInfo(Invoice invoice)
    {
        // 调用税务系统API验证发票真伪
        return TaxSystemAPI.VerifyInvoice(invoice);
    }
    
    private bool CheckFrequencyAbnormal(string sellerTaxId)
    {
        // 检测同一销售方开票频率是否异常
        var recentInvoices = _invoiceRepository
            .GetInvoicesBySeller(sellerTaxId, DateTime.Now.AddDays(-7));
        return recentInvoices.Count > 100; // 阈值可根据业务调整
    }
}

// 超期认证预警处理示例
class CertificationAlert {
  constructor() {
    this.alertThresholds = [30, 15, 7, 3]; // 预警阈值（天）
  }
  
  // 检查发票认证状态
  async checkCertificationStatus(invoices) {
    const today = new Date();
    const results = [];
    
    for (const invoice of invoices) {
      const daysRemaining = this.calculateRemainingDays(invoice.receiveDate);
      
      if (daysRemaining <= Math.max(...this.alertThresholds)) {
        const alertLevel = this.determineAlertLevel(daysRemaining);
        await this.sendAlert(invoice, alertLevel, daysRemaining);
        results.push({ invoiceId: invoice.id, alertLevel });
      }
    }
    
    return results;
  }
  
  // 计算剩余天数
  calculateRemainingDays(receiveDate) {
    const certificationDeadline = new Date(receiveDate);
    certificationDeadline.setDate(certificationDeadline.getDate() + 360); // 认证期限360天
    const timeDiff = certificationDeadline - new Date();
    return Math.ceil(timeDiff / (1000 * 3600 * 24));
  }
}

// 重复报销检测服务
public class DuplicateReimbursementService
{
    private readonly IInvoiceRepository _invoiceRepository;
    
    public DuplicateReimbursementService(IInvoiceRepository invoiceRepository)
    {
        _invoiceRepository = invoiceRepository;
    }
    
    public async Task<CheckResult> CheckDuplicateAsync(Invoice newInvoice)
    {
        // 基本查重：发票代码和号码
        var existingInvoice = await _invoiceRepository
            .FindByCodeAndNumberAsync(newInvoice.Code, newInvoice.Number);
            
        if (existingInvoice != null)
        {
            return new CheckResult { IsDuplicate = true, Reason = "完全相同发票已存在" };
        }
        
        // 高级查重：多维度相似度分析
        var similarInvoices = await _invoiceRepository
            .FindSimilarInvoicesAsync(newInvoice);
            
        if (similarInvoices.Any())
        {
            return new CheckResult { 
                IsDuplicate = true, 
                Reason = "找到高度相似发票", 
                SimilarInvoices = similarInvoices 
            };
        }
        
        return new CheckResult { IsDuplicate = false };
    }
}